The permanent alteration of the colour of keratinous fibres, in particular human hair, by the application of hair dyes is well known. In order to provide the consumer with the hair colour and the intensity of colour desired, a very complex chemical process is utilized. Permanent hair dyeing formulations typically comprise oxidative hair dye precursors, which can diffuse into the hair through the cuticle and into the cortex where they can then react with each other and suitable oxidising agents to form the end dye molecules. Due to the large size of these resultant molecules they are unable to readily diffuse out of the hair during subsequent washing with water and/or detergents; hence delivering the consumer-desired permanency of colour. The reaction typically takes place in an aggressive environment at approximately pH 10 in the presence of an alkalizing agent and in the presence of an oxidizing agent. Moreover, the consumer repeats this process regularly in order to maintain the desired hair colour shade and the intensity of colour and to ensure continual, even coverage of the hair including coverage of new hair growth.
However, despite the fact that commercial hair dyeing products have been available for many years, the products still exhibit a number of consumer-related deficiencies. In particular, the application of hair dye products is still a relatively time consuming process and it may take the consumer over an hour to mix, apply, wait for the colour to develop and remove the product; before drying and restyling. Since for most consumers the hair dyeing process is a regular part of their beauty routine it would be highly desirable if the time required to dye the hair could be reduced whilst still meeting all of the other requirements of; ease of application, low odour, and especially of course the delivery of the required hair colour, particularly for consumers requiring significant changes and/or levels of lift in the resultant colour.
A number of attempts have been described in the literature to reduce the application time required to dye hair, for example by the use of oxidative hair dye or bleach compositions comprising carbonate. For example;
WO01/28508 describes hair dyeing and bleaching compositions comprising an oxidising agent, hair colouring agents and ammonium carbonate and or carbamate which provides improved bleaching and colouring with reduced odour and hair damage without the need for buffering agents, pH modifiers or hair swelling agents. The compositions are applied to the hair for a time period of from 1 to 60 minutes.
FR1592939 describes a hair dyeing composition comprising oxidative dyes, ammonium carbonate and hydrogen peroxide at pH 7-9 which provides effective dyeing in a fairly short period of time.
EP435012 describes hair-dyeing compositions, which require a short dyeing time, create little damage to hair, and no irritating odour after dyeing comprising a carbonate source, a non odour generating alkali hydrogen peroxide and a buffer solution. Similarly, EP1106166 describes hair dye compositions comprising ammonia, carbonate (other than ammonia salt), transition metal salt and chelating agent which do not give off an irritating odour, have low skin irritation and can change the hair colour into a lighter tone in a short time.
WO04/014328 describes one step hair colouring compositions comprising peroxide oxidizing agents, specific oxidizing agents and at least one water soluble carbonate releasing salts which more effectively deliver colour wherein the composition is applied for a period of from 2 to 60 minutes.
Other attempted solutions have been described in U.S. Pat. No. 6,703,004 which describes hair bleaching compositions comprising an aqueous oxidising agent, persulphate, and a hydrophilic oil, in amounts sufficient to provide a mixture containing 3-5% active oxygen, and 0.7-1.2 meq/gm alkalinity, wherein the composition is capable of bleaching the hair in 10 to 30 minutes. Similarly, U.S. Pat. No. 6,669,933 describes an aqueous hair colouring composition for oxidatively colouring hair in less than 12 minutes comprising a dye and developer mixture, a free alkalinity concentration of 0.2-0.75 meq/gram and hydrogen peroxide.
US2004/0078906 describes a process for rapid dyeing and decolouration of keratin wherein a specific direct dye is applied to the fibres for a leave in time of less than 5 minutes.
Alternative attempts to reduce the application time of hair dyes on head involve methods which require short consecutive treatments of hair colourants whereby the colour change is achieved gradually after time. For example WO01/76546 describes a method of colouring hair comprising the steps of applying a hair colour altering composition to hair and leaving it on hair for about 0.5 to 15 minutes, wherein this method is repeated from once a month to about 3 times a day.
US2003/0154561 describes a method of applying an oxidative shampoo for a time period of from 5 seconds to 5 minutes whereby the treatment is repeated between 2 to 30 times and the time interval between treatments is 8 hrs to 30 days. Similarly, US2004/0098814 describes a method of permanently whereby the hair is subjected to a number of consecutive short treatments whereby the treatment comprises a dye intermediate in a shampoo or conditioner base, a water soluble carbonate releasing salt and a water soluble ammonium salt. US2004/0098816 also describes a method for the gradual permanent colouring of hair which includes subjecting the hair to a number of treatments having a set time interval between them, wherein the treatment compositions comprise ammonium carbonate in combination with a chelant.
However, none of these documents successfully address the problems associated with rapid hair colour delivery. In particular, the problem of hair damage resulting from the use of high concentrations of hydrogen peroxide and ammonia to provide the required lift and colour and similarly the problem of scalp irritation again typically due to the presence of a high concentration of hydrogen peroxide and ammonia and also the high pH value are not satisfactorily resolved with current technologies and marketed products.
Another critical problem with the rapid colour compositions of the prior art is the delivery of the required resultant colour and also the effective coverage of grey hair; the amount and distribution of which varies considerably from consumer to consumer. The prior art not only does not deliver the required shade and depth of colour, but, in particular, also fails to meet the needs of consumers wishing to lighten their hair colour by a number of levels of lift. The delivery of such lightening requires significant bleaching which is currently only provided by compositions comprising high levels of hydrogen peroxide and which are utilised over an extended period of time on the hair in order to provide the consumer with the desired colour outcome. Likewise, the prior art compositions also do not deliver uniform and even colour on the hair or maintain the initial colour coverage achieved during the post dyeing washing and drying cycle.
Hence, it would be further desirable to provide the consumer with a hair colourant, providing desired levels of lift and lightening, as well as improved colour delivery and reduced damage, reduced skin and scalp irritation and low odour which is effective over shorter time periods of application than currently available products and which can be used as part of the consumer's regular beauty care routine. Moreover, it would also be desirable to provide a rapid colour delivery system whereby the difficulty in applying the composition onto the hair in a quick but thorough manner is addressed.
It has now been surprisingly found that oxidative hair colouring compositions comprising an oxidising agent, a source of carbonate ions and an alkalising agent utilised at pH 9.5 and below provide a rapidly acting hair bleach or colourant that delivers the required colour requiring less than 20 minutes development time on the hair of the consumer, whilst still delivering the required colour as currently utilised ammonia/peroxide systems requiring 45 minutes waiting time. Moreover, the method of the present invention reduces damage to the hair, reduces skin and scalp irritation, has low odour and is compatible with current dye and dye precursor systems, resulting in improved lift and lightening for blonde shades, excellent dye deposition, uniformity and colour, particularly grey coverage, which is maintained over consumers wash and styling cycle until the next colouring treatment. The method also allows for quick actual application of the compositions to the hair and minimises staining of the consumers skin, particularly along the hair line, whilst delivering the desired colour.